Phase change inkjet printers receive phase change ink in a solid form, commonly referred to as ink sticks. Solid ink sticks are loaded into a printer and then melted to produce liquid ink that is used to form images on print media. Phase change inkjet printers form images using either a direct or an offset (or indirect) print process. In a direct print process, melted ink is jetted directly onto print media to form images. In an offset print process, melted ink is jetted onto a transfer surface, such as the surface of a rotating drum, belt, or band. Print media are moved proximate the surface of the rotating drum in synchronization with the ink images formed on the surface. The print media are then pressed against the surface on top of the ink images to transfer and affix the ink to the print media.
Offset phase change inkjet printers utilize drum maintenance systems to facilitate the transfer of ink images to the print media. Drum maintenance systems are typically configured to 1) lubricate the transfer surface with a very thin, uniform layer of release agent (e.g., silicone oil) before each print cycle, and 2) remove and store any excess oil, ink and debris from the surface of the drum after each print cycle.
To perform these functions, a drum maintenance system is usually equipped with a reservoir that contains a supply of release agent, and an applicator for delivering the release agent from the reservoir to the transfer surface. One or more elastomeric metering blades are also used to meter the release agent onto the transfer surface at a desired thickness and to divert excess release agent, residual ink left on the transfer surface, and other debris that may collect on the transfer surface to a reclaim area of the drum maintenance system. The collected release agent is filtered to enable its reuse in the printing system.
Over time, the ink material and debris collected in the drum maintenance system may combine with the release agent to form a high viscosity gel. As the gel accumulates in the system, the gel may adhere to the working edges of the elastomeric blade(s). The gel buildup on the blade(s) can impair metering performance. In some cases, the gel may adhere to the transfer surface and possibly cause print quality defects or inkjet contamination.